<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<style>
    .container{
        background: #f11;
        width: 200px;
        height: 200px;
        text-align: center;
        line-height: 200px;
    }
    .child{
        background-color: green;
        width: 100px;
        height: 100px;
        vertical-align: middle;
        display: inline-block;
        line-height: 100px;
    }
</style>
<body>
    <div class="container">
        <div class="child">11111</div>
    </div>
</body>
</html>